The present invention relates to a multistation press having several press stations arranged behind one another corresponding to a machining sequence.
Multistation presses are frequently constructed as an individual machine or as a system of presses which are directly linked with one another. This is particularly so if they operate in a given cycle in a mutually coordinated manner and are linked with one another by a transfer system which transports workpieces from one press station to the next. In this known type of press, the press stations are provided with tools which are set up for the respective workpiece type to be machined. Gripper devices are also provided on the transfer system for the special workpiece to be machined and to be transported.
If multistation presses are constructed for the machining of a special workpiece or are converted from the machining of one workpiece to the machining of another workpiece, the workpiece-specific parts of the press stations and of the transfer system must be exchanged. This should take place as fast and automatically as possible.
DE 38 43 975 C1 describes a transport device for larger workpieces for a transfer press. The transfer press has several press stations which are arranged along a transport direction, are spaced away from one another and in which bottom dies or bottom tools provided for receiving the workpieces are exchangeably arranged on sliding tables. Above the sliding tables, slides are provided which can be moved vertically up and down and which are driven synchronously. Each slide is equipped with a top tool and, together with the bottom tool arranged on the sliding table, defines a press station.
For the known workpiece transport, a cross-traverse transfer device is arranged between the press stations and has two mutually parallel transport rails. The transport rails are guided on both sides of the press stations along the entire length of the transfer press and are connected with one another by cross-traverses. Coupling devices detachably couple the cross-traverses are detachably connected with the transport rails. Between the press stations, so-called rig pins are arranged which are each connected in pairs with a sliding table and are used for receiving the cross-traverses to be exchanged. For the conversion, i.e., for exchanging the workpiece-specific parts of the press, the cross-traverses are deposited on the rig pins and are moved by the sliding tables laterally out of the press.
During the construction of this press, care must be taken that also the rig pins, which are arranged between the sliding tables and are each connected with a sliding table, can be moved laterally out of the press. For this reason, neither sliding tables nor rig pins connected with them can be arranged in the column area.
DE-PS 36 07 323 describes a press working line with individual presses in which the workpiece transport is carried out by gripper rails. To permit an automatic converting operation, the presses are equipped with sliding tables which can be moved in and out through the press columns of the press transversely to the transport direction of the parts. The respective sliding table permit the exchange of the tools which are used for machining the workpieces. The gripper rails provided for the transfer have part-related gripper rail parts which are each set up for the transport of the special part to be transported.
An exchange of these gripper rail parts is permitted by dividing each of the gripper rail parts into three parts which are detachably connected with the gripper rail. The gripper rail parts are equipped with the grippers which must be engaged with the respective workpiece while the continuous sections of the gripper rails are used only as supports for the gripper rail parts. The gripper rail parts are formed by one center part respectively as well as two exterior adjoining parts. Relative to the respective center part, the exterior parts are telescopically displaceable and are driven by piston-cylinder units.
For exchanging the gripper rail parts, the exterior parts are adjusted by the piston-cylinder units in the direction of the center part, after which the gripper rail parts forming a unit are deposited on a corresponding receiving device of the sliding table and are moved out of the press. The considerable weight of the gripper rails and of the piston-cylinder units driving them disadvantageously increases the weight of the gripper rails.
U.S. Pat. No. 5,248,288 describes a transfer press system which has several linked successive press stations by a cross-traverse transfer device. The cross-traverse transfer device has two parallel transport rails which are driven synchronously. Between the transport rails, cross-traverses are suspended transversely to the transport direction and are detachably connected with the transport rails by coupling devices. In each press station, a sliding table is provided by which the deforming tools can be moved laterally out of the press area. Each sliding table is equipped with a receiving device for cross-traverses detached from the transport rods which is arranged in a space defined by the adjacent sliding table. This receiving device contains two telescopic cylinders which, by way of a lever parallelogram, can be swivelled in parallel to the sliding table and can be height adjusted.
For the tool change, the receiving device takes the cross-traverses off the transport rails and folds the cross-traverses against the workpieces situated on the sliding table in order to achieve a compact arrangement of the tools to be exchanged. This manner of exchanging the gripper devices and the tools requires a transfer system with cross-traverses which requires spaces between the sliding tables.
DE 43 09 643 A12 describes a transfer device for the workpiece transfer which is constructed as a three-axis transfer. The transfer device is provided on a press with several press stations and has two transport rails extending at a distance parallel along the entire press length. These transport rails are synchronously moved in and against the transport direction, and are lifted and lowered as required by way of corresponding lifting devices. In addition, the transport rails can be moved toward and away from one another. The transport rails support carrier rails equipped with workpiece gripping devices. Depositing supports for receiving carrier rails are provided on each sliding table. In order to separate the carrier rails from the transport rails and place them on the depositing devices, particularly carrier rails situated in the column area are moved by the transport rails out of the column area and into the corresponding depositing position at the sliding tables and are deposited in a mutually aligned manner. In this position, the carrier rails with the sliding tables and the tools deposited thereon can be moved laterally out of the press.
Particularly in the case of presses with several columns which stand relatively close to one another, the passages required for the lateral moving out of the sliding tables are relatively limited with respect to their dimensions, and this can present problems.
It is an object of the present invention to provide a multistation press with a transfer device in which tools used for machining the workpieces, as well as gripper devices used for the transport of the workpieces and provided on the transfer device, can be automatically and simply exchanged without the requirement of additional space for moving the transport rails or for the lateral moving out of the sliding tables.
It is another object of the present invention to provide a process for changing the gripper devices during a tool change which meets the above-mentioned requirements.
These objects have been achieved in accordance with the present invention by providing a multistation press having a plurality of press stations arranged behind one another corresponding to a machining sequence; sliding tables associated with respective ones of the press stations; a transfer device for transporting workpieces between the press stations in a transport direction, and having at least two transport rails; a driving device for driving the transport rails to carry out a transfer movement; carrier devices detachably connected in a mutually spaced manner with the transport rails and provided with gripper devices; and at least one receiving device provided on the sliding table and arranged for connecting with the carrier devices, and for holding at least two separate carrier devices in spaced relationship to one another, wherein the carrier devices have a smaller distance from one another with respect to the distance on the transport rails.
In addition, the objects are achieved by a process for changing tools and gripper devices in press systems provided with sliding tables and with a workpiece transfer system, in which the workpiece transfer system has transport rails detachably connected with mutually separate carrier devices carrying gripper devices, comprising the steps of bringing a receiving device provided on the sliding table to the sliding table in a movement directed laterally to a transport direction defined by the workpiece flow; bringing the carrier device to a receiving point of the receiving device by a movement of the transport rail to be coupled therewith; detaching the transport rail from the carrier device which is now carried by the receiving device; bringing another carrier device to another receiving point of the receiving device by another movement of the transport rail to be coupled therewith, whereby the receiving points are adjacent each other; detaching the transport rail from the another carrier device which is now carried by the receiving device; moving the receiving device away by the sliding table; and moving the sliding table, which carries the tool and the carrier device, laterally out of a working range of the press system.
The multistation press of the present invention which may be an individual machine or a sequence of several presses linked with one another by the transfer device, is provided with sliding tables which can be moved laterally out of the press and permit a quick tool change. The transfer device has two mutually parallel transport rails which support mutually spaced carrier devices which, in turn, are provided with gripper devices for the workpieces. The carrier devices can be detached from the transport rails, with receiving devices for receiving the carrier rails are arranged on the sliding tables.
The carrier devices are each arranged on the transport rails in a mutually spaced manner, and the receiving devices of the sliding tables are constructed such that the carrier devices can be deposited close to one another, in which case they are not aligned with one another. Two carrier devices which are mutually adjacent on the transport rail carry out a longitudinal stroke during the transfer movement which longitudinal stroke corresponds to their respective own length plus the distance to the respective next adjacent carrier device.
Both carrier devices can be housed on the sliding table in an area whose longitudinal course measured in the transport direction does not exceed the stroke width and is preferably maximally as long as a single carrier device. This can be achieved particularly by an overlapping arrangement of the carrier devices in that these are, for example, stacked above one another. Such a housing of the carrier devices permits the receiving of additional carrier devices which will be required particularly if intermediate depositing devices are arranged between the sliding tables Each transport rail will then support two carrier devices per sliding table.
As a result of the receiving of the carrier devices on the sliding tables which saves space in the longitudinal direction, carrier devices situated in the column area are movable by a longitudinal stroke movement of the transport rails out of the column area to be deposited on corresponding holding devices of the sliding table in a mutually overlapping manner. A sliding table can receive on each side, for example, two carrier devices arranged above one another which do not project beyond the sliding table. It can, therefore, be moved without any problems laterally out of the press area even if the passage provided for this purpose is restricted by adjacent press columns.
Furthermore, no devices are required for providing the carrier devices with a longitudinal movement with respect to the transport rails. Thereby, the mass of the carrier devices and transport rails and thus the occurring accelerating and braking forces remain within limits. This is a particular advantage in view of the transport rail driving device.
A particularly space-saving arrangement of the carrier devices on the sliding tables is obtained if the carrier devices are parallel to one another, either next to one another or above one another. If, in this case, the carrier devices each have a low height, the vertical adjustability of the transport rail, which exists anyhow, will be sufficient for depositing the carrier device on the receiving devices. This preferably takes place without providing driving devices on the carrier devices. That is, the carrier devices have a purely passive construction which keeps their weight comparatively low.
For fastening the carrier rail on the transport rail, a locking device is preferably arranged to act between them and has the purpose of coupling the gripper devices during the normal operation of the transfer device, i.e., during the workpiece transfer, stationarily to the transport rails. As soon as the carrier device is received by the receiving device and is form-lockingly connected therewith, the locking device will change into the release position. As a result of a suitable longitudinal movement, the transport rail can detach and separate from the carrier device.
The receiving device, which can, for example, also be rigid, is preferably swivellably disposed at the sliding table. Thereby, after the transfer of the carrier devices has taken place, the receiving device can be laterally swivelled away so that the gripper devices can be moved out of the tool range and the carrier devices can be moved out of the moving range of the transport rail.
The transfer unit which is formed by the transport rails of the driving unit and the gripper devices is preferably constructed as a three-axis transfer. The transport rails are arranged parallel to one another as well as parallel to the transport direction and can be moved in, the transport direction; i.e., horizontally, vertically as well as toward and away from one another. In such a three-axis transfer, the transferring of the carrier devices held by the transport rails to the corresponding receiving devices on the sliding tables can be carried out in a particularly simple manner using the three-axis transfer for the fetching and the suspending of the carrier devices in the receiving devices without the aid of additional driving units.
A transport rail allows the first one of the carrier devices received by the holding device to be first inserted into the holding device by a lateral depositing movement. Thereafter, the transport rail is separated from the carrier device preferably by a combined advancing/lowering movement. Then the transport rail brings the additional carrier device to be connected with the holding device and deposits it thereon. The carrier devices can be held close to one another and therefore held in a very space-saving manner on the sliding table.